
\begin{tikzpicture}[scale=1.6]
  \coordinate[label=left:$A$] (A) at (160:1);
  \coordinate[label=below:$C$] (C) at (-50:1);
  \coordinate[label=below:$O$] (O) at (0,0);
  \coordinate[label=right:$P$] (P) at ($ (C)!2.5! -90:(O) $);
  \draw[name path=AP] (A) -- (P);
  \draw[name path=circ] (O) circle (1);
  \path[name intersections={of=AP and circ}]
    coordinate[label=above right:$B$] (B) at (intersection-1);
  \fill (O) circle (.5pt);
  \draw ($ (P)!1.5!(C) $) -- (P) -- (A);
\end{tikzpicture}
